Ion observations from geosynchronous orbit as a proxy for ion cyclotron wave growth during storm times

Abstract

[1] There is still much to be understood about the processes contributing to relativistic electron enhancements and losses in the radiation belts. Wave particle interactions with both whistler and electromagnetic ion cyclotron (EMIC) waves may precipitate or accelerate these electrons. This study examines the relation between EMIC waves and resulting relativistic electron flux levels after geomagnetic storms. A proxy for enhanced EMIC waves is developed using Los Alamos National Laboratory Magnetospheric Plasma Analyzer plasma data from geosynchronous orbit in conjunction with linear theory. In a statistical study using superposed epoch analysis, it is found that for storms resulting in net relativistic electron losses, there is a greater occurrence of enhanced EMIC waves. This is consistent with the hypothesis that EMIC waves are a primary mechanism for the scattering of relativistic electrons and thus cause losses of such particles from the magnetosphere.Citation: Blum, L. W., E. A. MacDonald, S. P. Gary, M. F. Thomsen, and H. E. Spence (2009), Ion observations from geosynchronous orbit as a proxy for ion cyclotron wave growth during storm times,

Science Goals and Overview of the Radiation Belt Storm Probes (RBSP) Energetic Particle, Composition, and Thermal Plasma (ECT) Suite on NASA’s Van Allen Probes Mission

“…Thomsen et al 1998;Jordanova et al 2003;Blum et al 2009). Additionally, the HOPE instrument will provide ion composition measurements (at the same energies as MPA) currently unavailable to modelers.…”

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

“…where α h ¼ a 0 À a 1 ln n hp n e À a 2 ln n hp n e 2 and a 0 = 0.409, a 1 = 0.0145, and a 2 = 0.00028 [Blum et al, 2009]. The parallel plasma beta of energetic H + β ||h = 2μ 0 n hp kT || /B 2 .…”

“…The electron density is n e . The constants σ 0 = 0.429, σ 1 = 0.124, and σ 2 = 0.0118 were derived by Blum et al [2009] by assuming that the local wave growth rate (γ/Ω p ) is 0.001 and fitting linear theory results to Los Alamos National Laboratory (LANL) Magnetospheric Plasma Analyzer observations at geosynchronous orbit (GEO). Those constants are still valid at places other than GEO.…”

High-speed stream driven inferences of global wave distributions at geosynchronous orbit: relevance to radiation-belt dynamics

“…Generally, for the magnetospheric ion and electron populations used in this study, a maximum growth rate of 0.001 is appropriate to choose (e.g. MacDonald et al 2008;Blum et al 2009a). EMIC-mode waves are excited by the free energy in the hot (keV) plasmasheet ions.…”

“…In this paper, we use geosynchronous observations of the unstable plasma-sheet ion and electron populations that produce whistler and EMIC waves to infer the probable occurrence properties of such waves in association with high-speed stream events. The 'inference technique' has been well established (MacDonald et al 2008;Blum et al 2009a), and is based on an extensive theoretical and modelling framework (e.g. Gary 1993;Gary et al 1994;Gary & Wang 1996).…”